Dimming unit, and liquid crystal display device

ABSTRACT

The present invention relates to a dimming unit including: a dimming panel; and drive circuitry, the dimming panel sequentially including a first substrate, a liquid crystal layer, and a second substrate, the first substrate sequentially including an insulating substrate, a lower-layer electrode, a first insulating layer, multiple first electrodes, a second insulating layer, and a second electrode which is provided with multiple parallel linear electrodes and to which a constant voltage is applied, the first electrodes including multiple island electrodes which are spaced from each other in a plan view and are electrically connected to each other, at least one of the island electrodes being electrically connected to the lower-layer electrode through a contact hole, the drive circuitry controlling voltages applied to the respective first electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to U.S.provisional Patent Application No. 63/002,387 filed on Mar. 31, 2020,the contents of which are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to dimming units and liquid crystaldisplay devices including the dimming unit.

Description of Related Art

Dimming panels are panels that can control the transmittance of light inresponse to the voltage applied to the panel. For example, a dimmingpanel can be used as an optical member that is placed between animage-providing liquid crystal panel and a backlight and controls theamount of backlight illumination transmitted, or as a member thatcontrols the amount of external light transmitted into a building, avehicle, or the like. One of dimming methods using such a dimming panelincludes preparing a liquid crystal composition sealed between a pair ofsubstrates and applying a voltage to the liquid crystal composition andthereby changing the alignment of liquid crystal molecules andcontrolling the amount of light transmitted through the dimming panel. Adevice including the dimming panel and control circuitry for controllingthe dimming panel is also referred to as a dimming unit.

Liquid crystal display devices are display devices utilizing a liquidcrystal composition to display images. In a typical display modethereof, a liquid crystal panel containing a liquid crystal compositionbetween a pair of substrates is irradiated with light from a backlightand voltage is applied to the liquid crystal composition to change thealignment of liquid crystal molecules, whereby the amount of lighttransmitted through the liquid crystal panel is controlled. Such liquidcrystal display devices have advantageous features such as thin profile,light weight, and low power consumption, and are therefore used inelectronic devices such as televisions, smartphones, tablet PCs, andautomotive navigation systems.

A study on liquid crystal display devices has been made for achieving auniform luminance distribution on the light emitting surface of abacklight by disposing a dimming panel between an image-providing liquidcrystal panel and the backlight. For example, WO 2008/053724 discloses aliquid crystal display device including: an image-providing panel thatincludes a liquid crystal display panel; a light source for illuminatingthe liquid crystal display panel; and a dimming panel disposed betweenthe image-providing panel and the light source, the dimming panelincluding a transmissive liquid crystal display panel and performinggray scale display based on luminance information in a video imagesignal input to the image-providing panel, wherein the dimming panelincludes pixels having a size greater than pixels constituting theimage-providing panel. The “pixels constituting the dimming panel” in WO2008/053724 correspond to “dimming units” herein. The “dimming units”will be described later.

BRIEF SUMMARY OF THE INVENTION

A study on methods for displaying a high quality image has been madeaiming to develop a liquid crystal display device capable of performinghigh dynamic range (HDR) imaging. The HDR imaging enables display of aclearer image with a wider brightness range than an image with aconventional dynamic range (standard dynamic range, SDR). In order todisplay an image with a wider brightness range by HDR imaging, theliquid crystal display device is required to have an increased maximumluminance and an increased contrast ratio.

A method for increasing the contrast ratio of a liquid crystal displaydevice includes dividing the light emitting surface of a backlight intomultiple illuminating areas and separately driving these areas (localdimming). Unfortunately, the illuminating areas for local dimming have asignificantly greater size than the pixel size of the image-providingliquid crystal panel. This may result in a halo phenomenon that causes aportion which should be displayed dark to look brightly at a boundarybetween images with a large difference in brightness.

The present inventors studied another method for increasing the contrastratio of a liquid crystal display device, including disposing a dimmingpanel between an image-providing liquid crystal panel and a backlight.The study demonstrated that provision of a dimming panel can control theamount of light emitted from the backlight (hereinafter, also referredto as backlight illumination) and transmitted through each dimming unitconstituting the dimming panel, which can reduce the halo phenomenonwhile increasing the contrast ratio of the liquid crystal displaydevice.

Sophisticated large displays used for a master monitor or the like havebeen developed recently. When a dimming panel is applied to such asophisticated display, excellent viewing angle characteristics arerequired not only for the image-providing liquid crystal panel but alsofor the dimming panel.

Examples of a dimming panel having excellent viewing anglecharacteristics include horizontally aligned dimming panels. Forexample, a horizontally aligned dimming panel has a structure includinga first substrate provided with a first electrode and a second electrodewith an insulating layer in between, a second substrate disposedopposite the first substrate, and a liquid crystal layer sealed betweenthe first substrate and the second substrate. The horizontally aligneddimming panel controls the amount of light transmitted through thedimming panel by changing the alignment azimuth of liquid crystalmolecules in the liquid crystal layer with an electric field formedbetween the first electrode and the second electrode. One of the firstelectrode and the second electrode is an electrode for applying apredetermined voltage to each dimming unit (hereinafter, also referredto as a dimming unit electrode) and the other is an electrode forapplying a constant voltage to the entire dimming panel beyond theboundaries of the dimming units. Preferably, at least one of the dimmingunit electrode or the electrode for applying a constant voltage to theentire dimming panel includes multiple linear electrodes and thereby canform an electric field with the other electrode through the spaces(slits) between the linear electrodes.

A study made in WO 2008/053724 is that in order to smooth the luminancedifference between dimming units, the boundary between adjacent dimmingunits constituting the dimming panel is made irregular (zigzag) andthereby the luminance distribution is smoothly changed. According tostudies by the present inventors, however, in a horizontally aligneddimming panel, making a boundary between dimming units zigzag asdisclosed in WO 2008/053724 fails to smoothly change the luminancedistribution and rather causes zigzag dark lines. When a dimming panelhaving an unsmooth luminance distribution provides images of differentscales in adjacent dimming units, the luminance difference between thedimming units unfortunately becomes remarkable. Dimming unitsconstituting a dimming panel are larger than the pixels constituting theimage-providing liquid crystal panel, and thus the outlines thereof areunintendedly recognized in some cases when the dimming panel is stackedon the image-providing liquid crystal panel. Studies by the presentinventors further revealed that in display with a horizontally aligneddimming panel, liquid crystal molecules possibly have an alignmentdefect at the boundaries between dimming units and thereby cause darklines. Appearance of such dark lines emphasizes the boundaries betweendimming units, and thereby not only reduces the display quality of thedimming panel but also reduces the transmittance of the dimming panel.

There is room for studying the electrode shape at the boundary betweenadjacent dimming units in order to smooth the luminance distributionbetween adjacent dimming units. Unfortunately, in the case of providingmultiple linear electrodes to the dimming unit electrode, it isdifficult to form the linear electrodes with a complicated electrodeshape for each dimming unit while satisfying the electrode width andslit width capable of forming a fringe electric field.

In addition to serving as a member of a liquid crystal display device asdescribed above, the dimming panel by itself can serve as an anti-glarepanel that controls the amount of external light transmitted. When suchan anti-glare panel used as a vehicle-mounted sun visor, for example,has dark lines at boundaries between dimming units, the dark linesinterrupt the passenger's view. Thus, a dimming panel that sufficientlyrestricts the occurrence of dark lines is awaited.

The present invention is made under the current situation in the art andaims to provide a dimming unit that allows a complicated electrode shapedesign and has a high transmittance and a smooth change in luminancedistribution, and a liquid crystal display device including the dimmingunit.

(1) One embodiment of the present invention is directed to a dimmingunit including: a dimming panel; and drive circuitry, the dimming panelsequentially including a first substrate, a liquid crystal layer, and asecond substrate, the first substrate sequentially including aninsulating substrate, a lower-layer electrode, a first insulating layer,multiple first electrodes, a second insulating layer, and a secondelectrode which is provided with multiple parallel linear electrodes andto which a constant voltage is applied, the first electrodes includingmultiple island electrodes which are spaced from each other in a planview and are electrically connected to each other, at least one of theisland electrodes being electrically connected to the lower-layerelectrode through a contact hole, the drive circuitry controllingvoltages applied to the respective first electrodes.

(2) In an embodiment of the present invention, the dimming panelincludes the structure (1), the island electrodes are arranged in amanner that an electrode area occupancy decreases toward an outerperiphery of each of the first electrodes, at least one of the islandelectrodes of a selected electrode of the first electrodes is disposedin a position between the island electrodes of a next electrode, and atleast one of the island electrodes of the next electrode is disposed ina position between the island electrodes of the selected electrode.

(3) In an embodiment of the present invention, the dimming panelincludes the structure (2), and the lower-layer electrode overlaps aspace between the island electrodes of the selected electrode and theisland electrodes of the next electrode in a plan view.

(4) In an embodiment of the present invention, the dimming panelincludes any one of the structures (1) to (3), and at least one of theisland electrodes has a quadrangular planar shape.

(5) In an embodiment of the present invention, the dimming panelincludes any one of the structures (1) to (4), and at least one of theisland electrodes has an outer peripheral shape including a linearportion that forms an angle of −30° to +30° with respect to an extendingdirection of the linear electrodes of the second electrode, providedthat in a view seen from a second substrate end, an angle formed in aclockwise direction is defined to be a negative angle and an angleformed in a counterclockwise direction is defined to be a positiveangle.

(6) In an embodiment of the present invention, the dimming panelincludes any one of the structures (1) to (3), and at least one of theisland electrodes has a planar shape including a curved portion.

(7) In an embodiment of the present invention, the dimming panelincludes any one of the structures (1) to (6), and the first substrateincludes multiple connection lines connecting the respective firstelectrodes and the drive circuitry.

(8) In an embodiment of the present invention, the dimming panelincludes any one of the structures (1) to (7), each of the firstelectrodes further includes a base electrode provided with multipleapertures, the island electrodes surround the base electrode in a planview, the base electrode is electrically connected to the lower-layerelectrode through another contact hole, at least one of the islandelectrodes of a selected electrode of the first electrodes is disposedin a position inside at least one of the apertures of a next electrode,and at least one of the island electrodes of the next electrode isdisposed in a position inside at least one of the apertures of theselected electrode.

(9) In an embodiment of the present invention, the dimming panelincludes the structure (8), and the apertures provided in the baseelectrode are arranged in a manner that an aperture area occupancyincreases from a center toward an outer periphery of the base electrode.

(10) In an embodiment of the present invention, the dimming panelincludes the structure (8) or (9), and the lower-layer electrodeoverlaps a space between the apertures provided in the base electrode ofthe selected electrode and the island electrodes of the next electrodein a plan view.

(11) In an embodiment of the present invention, the dimming panelincludes any one of the structures (8) to (10), and at least one of theapertures has a quadrangular outer peripheral shape.

(12) In an embodiment of the present invention, the dimming panelincludes any one of the structures (8) to (11), and the at least oneaperture has an outer peripheral shape including a linear portion thatforms an angle of −30° to +300 with respect to an extending direction ofthe linear electrodes of the second electrode, provided that in a viewseen from a second substrate end, an angle formed in a clockwisedirection is defined to be a negative angle and an angle formed in acounterclockwise direction is defined to be a positive angle.

(13) In an embodiment of the present invention, the dimming panelincludes any one of the structures (8) to (10), and at least one of theapertures includes an outer peripheral shape including a curved portion.

(14) One embodiment of the present invention is directed to a liquidcrystal display device including: an image-providing liquid crystalpanel; a backlight; and a dimming unit between the image-providingliquid crystal panel and the backlight, the dimming unit including: adimming panel; and drive circuitry, the dimming panel sequentiallyincluding a first substrate, a liquid crystal layer, and a secondsubstrate, the first substrate sequentially including an insulatingsubstrate, a lower-layer electrode, a first insulating layer, multiplefirst electrodes, a second insulating layer, and a second electrodewhich is provided with multiple parallel linear electrodes and to whicha constant voltage is applied, the first electrodes including multipleisland electrodes which are spaced from each other in a plan view andare electrically connected to each other, at least one of the islandelectrodes being electrically connected to the lower-layer electrodethrough a contact hole, the drive circuitry controlling voltages appliedto the respective first electrodes.

(15) In an embodiment of the present invention, the dimming panelincludes the structure (14), the image-providing liquid crystal panelincludes multiple pixels including sub-pixels of multiple colors andbeing arranged in a matrix in a plane, and the island electrodes includean overlapping electrode portion overlapping the sub-pixels of allcolors included in one pixel.

(16) In an embodiment of the present invention, the dimming panelincludes the structure (15), and in the overlapping electrode portion, adifference between a maximum value and a minimum value among electrodeareas overlapping the respective sub-pixels of the respective colors is30% or less of the maximum value.

(17) In an embodiment of the present invention, the dimming panelincludes the structure (14) or (15), the image-providing liquid crystalpanel includes multiple pixels including sub-pixels of multiple colorsand being arranged in a matrix in a plane, and the apertures include anoverlapping aperture portion overlapping the sub-pixels of all colorsincluded in one pixel.

(18) In an embodiment of the present invention, the dimming panelincludes the structure (17), and in the overlapping aperture portion, adifference between a maximum value and a minimum value among apertureareas overlapping the respective sub-pixels of the respective colors is30% or less of the maximum value.

The present invention can provide a dimming unit that allows acomplicated electrode shape design and has a high transmittance and asmooth change in luminance distribution, and a liquid crystal displaydevice including the dimming unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a liquid crystal displaydevice of Example 1.

FIG. 2 is a schematic cross-sectional view showing a part of a dimmingpanel used in Example 1.

FIG. 3 is a schematic plan view showing one of first electrodes used inthe dimming panel of Example 1.

FIG. 4 is a schematic plan view showing a part of the dimming panel usedin Example 1.

FIG. 5A is a partially enlarged schematic plan view showing an exampleof island electrodes shown in FIG. 3.

FIG. 5B is a partially enlarged schematic plan view showing anotherexample of island electrodes shown in FIG. 3.

FIG. 6 is a plan view showing an arrangement example of first electrodeswith reference to pixels of an image-providing liquid crystal panel.

FIG. 7 is a schematic view for describing a manner for reducing theelectrode area of the island electrodes in Example 1.

FIG. 8 is a schematic plan view showing an example of disposing anoverlapping electrode portion with reference to one pixel in Example 1.

FIG. 9 is a schematic plan view showing a preferred example of disposingan overlapping electrode portion with reference to one pixel in Example1.

FIG. 10 is a schematic plan view showing an example of disposing anoverlapping aperture portion for each pixel in Example 1.

FIG. 11 is a schematic plan view showing a preferred example ofdisposing an overlapping aperture portion for each pixel in Example 1.

FIG. 12 is a schematic plan view of the second electrode shown in FIG.2.

FIG. 13 is a schematic plan view of the dimming panel, showing anexample of a method for driving the first electrodes in Example 1.

FIG. 14 is a schematic graph showing a change in luminance distributionof the dimming panel used in the liquid crystal display device ofExample 1.

FIG. 15 is a schematic plan view showing one of first electrodes used ina dimming panel of Example 2.

FIG. 16 is a plan view of first electrodes arranged with reference tothe pixels of the image-providing liquid crystal panel.

FIG. 17 is a schematic plan view showing an arrangement example of firstelectrodes shown in FIG. 15.

FIG. 18 is a schematic plan view of the dimming panel in Example 2,showing an example of a method for driving the first electrodes.

FIG. 19 is a schematic plan view showing one of first electrodes used ina dimming panel of Example 3.

FIG. 20 is a partially enlarged schematic plan view showing an exampleof island electrodes shown in FIG. 19.

FIG. 21 is a schematic plan view showing an arrangement example of firstelectrodes shown in FIG. 19.

FIG. 22 is a schematic view for describing a manner for reducing theelectrode area of the island electrodes in Example 3.

FIG. 23 is a schematic plan view showing an example of disposing anisland electrode with reference to one pixel in Example 3.

FIG. 24 is a schematic plan view showing a preferred example ofdisposing island electrodes with reference to one pixel in Example 3.

FIG. 25 is a schematic plan view showing an example of disposingapertures in base electrodes in Example 3.

FIG. 26 is a schematic plan view showing a preferred example ofarranging apertures in base electrodes in Example 3.

FIG. 27A is an enlarged schematic plan view of a boundary portionbetween adjacent first electrodes shown in FIG. 21.

FIG. 27B is an enlarged schematic view for describing an islandelectrode shown in FIG. 27A.

FIG. 27C is an enlarged schematic view for describing an aperture shownin FIG. 27A.

FIG. 28 is a schematic plan view showing an example of disposing alower-layer electrode in Example 5.

FIG. 29 is a schematic cross-sectional view of the first substrate shownin FIG. 28.

FIG. 30 is an enlarged schematic cross-sectional view showing a part ofFIG. 29.

FIG. 31 is a schematic plan view of the planar shape of segmentelectrodes used in a dimming panel of Comparative Example 1.

FIG. 32 is an enlarged schematic view showing a boundary portion betweenadjacent segment electrodes shown in FIG. 31.

FIG. 33 is a schematic cross-sectional view of the dimming panel used inComparative Example 1.

FIG. 34 is a schematic graph showing a change in luminance distributionof the dimming panel used in the liquid crystal display device ofComparative Example 1.

FIG. 35 is a plan photograph of the dimming panel used in ComparativeExample 1.

FIG. 36 is an enlarged photograph showing a part of FIG. 35.

FIG. 37 is a schematic plan view for describing a 176° portion of FIG.36.

FIG. 38 is a schematic plan view for describing an 86° portion of FIG.36.

FIG. 39 is a view showing a relation between gap angles and occurrenceof dark lines shown in FIG. 36.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a dimming unit and a liquid crystal display deviceaccording to an embodiment of the present invention are described. Theembodiment, however, is not intended to limit the scope of the presentinvention. The design may be modified as appropriate within the rangesatisfying the configuration of the present invention.

<Dimming Unit>

A dimming unit according to an embodiment of the present inventionsequentially includes: a dimming panel; and drive circuitry, the dimmingpanel sequentially including a first substrate, a liquid crystal layer,and a second substrate, the first substrate sequentially including aninsulating substrate, a lower-layer electrode, a first insulating layer,multiple first electrodes, a second insulating layer, and a secondelectrode which is provided with multiple parallel linear electrodes andto which a constant voltage is applied, the first electrodes includingmultiple island electrodes which are spaced from each other in a planview and are electrically connected to each other, at least one of theisland electrodes being electrically connected to the lower-layerelectrode through a contact hole, the drive circuitry controllingvoltages applied to the respective first electrodes.

The dimming panel sequentially includes a first substrate, a liquidcrystal layer, and a second substrate. The first substrate sequentiallyincludes an insulating substrate, a lower-layer electrode, a firstinsulating layer, multiple first electrodes, a second insulating layer,and a second electrode which includes parallel linear electrodes and towhich a constant voltage is applied. In other words, the dimming panelis a horizontally aligned dimming panel. A horizontally aligned dimmingpanel has excellent viewing angle characteristics and is thus suitablyused for a large liquid crystal display device such as a master monitorthat is required to have high display quality.

The following describes a dimming method using the dimming panel. When aconstant voltage is applied to the second electrode and the drivingcircuitry applies predetermined voltages to the respective firstelectrodes, an electric field is formed in the liquid crystal layer. Thesecond electrode includes parallel linear electrodes. Thus, a fringeelectric field is formed between the first electrodes and the linearelectrodes and thereby changes the alignment azimuth of liquid crystalmolecules in the liquid crystal layer. The dimming panel may besandwiched between a pair of linear polarizers. The linear polarizersmay be disposed with their absorption axes being perpendicular to eachother. Forming an angle between the alignment azimuth of the liquidcrystal molecules and the absorption axis of each linear polarizerenables controlling the amount of backlight illumination transmittedthrough the dimming panel and thereby can provide gray scale display.The polarizer placed on the image-providing liquid crystal panel end mayalso serve as one of paired polarizers sandwiching the image-providingliquid crystal panel.

A structure in which a constant voltage is applied to the secondelectrode provided with the linear electrodes and each first electrodeapplies a predetermined voltage to the corresponding dimming uniteliminates the need for providing linear electrodes for forming a fringeelectric field in the first electrode and thus allows the firstelectrodes to have any electrode shape as long as an electric field canbe formed with the second electrode. Accordingly, a complicatedelectrode shape such as a shape including multiple island electrodes canbe formed as described below. According to the studies by the presentinventors, in a diming panel that includes as a dimming unit electrodean electrode provided with multiple linear electrodes and as a solidelectrode an electrode that applies a constant voltage to the entiredimming panel, for example, the extending direction of the linearelectrodes, the electrode width of the linear electrodes, and the slitwidth between the linear electrodes need to be designed within a rangewhere a fringe electric field can be formed with the solid electrode.Thus, the dimming unit electrode has limitation for its design, whichmakes it difficult to form a complicated electrode shape such as theshape including multiple island electrodes.

The linear electrodes of the second electrode may form an angle of 75°or greater and 85° or smaller with the absorption axis of one of thepolarizers sandwiching the dimming panel. The second electrode may bedisposed on the entire dimming panel beyond the boundaries betweendimming units. For example, a predetermined reference voltage may beapplied to the second electrode or the second electrode may be grounded.

The liquid crystal layer contains liquid crystal molecules. The liquidcrystal molecules may have a positive anisotropy of dielectric constant(Δε) (positive type) or a negative anisotropy of dielectric constant(negative type) defined by the following formula. The liquid crystalmaterial used in the liquid crystal layer of the dimming panel may bethe same as or different from the liquid crystal material used in theliquid crystal layer of the image-providing liquid crystal paneldescribed later. In order to improve the reliability, the liquid crystalmaterial used in the liquid crystal layer of the dimming panelpreferably has better resistance to high temperature and high luminancethan the liquid crystal material used in the liquid crystal layer of theimage-providing liquid crystal panel.

Δε=(dielectric constant in major axis direction of liquid crystalmolecules)−(dielectric constant in minor axis direction of liquidcrystal molecules)  (L)

The first electrodes each include multiple island electrodes that arespaced from each other in a plan view and are electrically connected toeach other. At least one island electrode is electrically connected tothe lower-layer electrode through a contact hole. Regions provided withthe respective first electrodes in a plan view are herein referred to asdimming units. In other words, the dimming panel includes multipledimming units arranged in an in-plane direction. In a plan view, theisland electrodes seem to be scattered with a specific distance inbetween. Actually, the lower-layer electrode electrically connects theisland electrodes. Thus, the same voltage can be applied to the islandelectrodes constituting one first electrode. The first electrodesincluding island electrodes can smooth the change in gray scaledistribution between adjacent dimming units. The island electrodes mayeach be electrically connected to the lower-layer electrode through thecontact holes.

The drive circuitry controls voltages applied to the respective firstelectrodes. In the case where a predetermined reference voltage isapplied to the second electrode, the drive circuitry may control theconstant voltage applied to the second electrode.

The island electrodes may be arranged in a manner that the electrodearea occupancy decreases toward the outer periphery of the firstelectrode. The electrode area occupancy refers to the proportion of thetotal electrode area of island electrodes in a predetermined unit areain one dimming unit. The arrangement of the island electrodes in amanner that the electrode area occupancy thereof decreases toward theouter periphery of the first electrode in a plan view allows the centerportion of the first electrode to have the highest luminance and allowsthe luminance to moderately decrease toward the outer periphery. Theelectrode area occupancy may be decreased by arranging the islandelectrodes in a manner that the electrode area decreases toward theouter periphery of the first electrode or by reducing the number ofisland electrodes toward the outer periphery of the first electrode. Theouter periphery of the first electrode corresponds to a line connectingthe island electrodes disposed at the farthest positions from the centerof the first electrode in a plan view. The outer periphery of the baseelectrode may not be a linear periphery and may have an irregularportion.

At least one island electrode included in a selected electrode of thefirst electrodes may be disposed in a position between adjacent two ofthe island electrodes of in a next electrode, and at least one islandelectrode included in the next electrode may be disposed in a positionbetween adjacent two of the island electrodes of the selected electrode.Such an arrangement smooths the change in luminance distribution betweenadjacent first electrodes and thereby allows the boundary betweenregions with the first electrodes (dimming units) to be lessrecognizable. In other words, provided that one of the adjacent firstelectrodes is defined as an electrode A and the other thereof is definedas an electrode B, the region with the electrode A (dimming unit A) andthe region with the electrode B (dimming unit B) are overlapped.

The island electrodes are spaced from each other in a plan view. Thus,part of island electrodes of the electrode A can be disposed betweenisland electrodes of the electrode B. Similarly, part of islandelectrodes of the electrode B can be disposed between island electrodesof the electrode A. The island electrodes of the electrode A may bearranged in a manner that the electrode area occupancy decreases fromthe center of the electrode A toward the center of the electrode B, andthe island electrodes of the electrode B may be arranged in a mannerthat the electrode area occupancy decreases from the center of theelectrode B toward the center of the electrode A. For example, theisland electrodes of the electrode A may be arranged in a manner thatthe electrode area decreases from the center of the electrode A towardthe center of the electrode B, and the island electrodes of theelectrode B may be arranged in a manner that the electrode areadecreases from the center of the electrode B toward the center of theelectrode A. Alternatively, the island electrodes of the electrode A maybe arranged in a manner that the number of electrodes decreases from thecenter of the electrode A toward the center of the electrode B, and theisland electrodes of the electrode B may be arranged in a manner thatthe number of electrodes decreases from the center of the electrode Btoward the center of the electrode A.

The lower-layer electrode may overlap spaces between the islandelectrodes of the selected electrode and the island electrodes of thenext electrode in a plan view. The boundary portion between theelectrode A and the electrode B may have inactive liquid crystalmolecules as a result of receiving both influences of an electric fieldformed between the electrode A and the second electrode and of anelectric field formed between the electrode B and the second electrode,and thereby have an alignment defect which may be recognized as a darkline. Disposing the lower-layer electrode to overlap a space between theelectrode A and the electrode B in a plan view can form an electricfield between the lower-layer electrode and the second electrode. Thiselectric field can change the alignment of liquid crystal molecules inthe boundary portion between the electrode A and the electrode B andthereby can restrict the occurrence of a dark line. This structure thuscan restrict a reduction in display quality caused by dark lines and canincrease the luminance of the dimming panel. The lower-layer electrodemay be formed in a cyclic shape along the outer periphery formed byconnecting outer island electrodes.

The first substrate may include multiple connection lines connecting therespective first electrodes and the drive circuitry. In other words,preferably, the first electrodes are connected to the drive circuitrythrough the respective connection lines and are driven in a segmentdriving mode in which the voltages applied to the respective firstelectrodes are separately controlled. An example of other drivingmethods is a matrix driving mode in which a switching element such as aTFT is disposed in each dimming unit and a voltage applied to the firstelectrodes is controlled for each dimming unit. In the matrix drivingmode, the first electrodes are to be charged in a short period of timesuch as one horizontal scan period. Thus, in a dimming panel used for alarge liquid crystal display device such as in particular a 30-inchdisplay, metal lines formed from a metal material with high electricalconductivity, such as copper, aluminum, titanium, or molybdenum, aresuitably used for members connected to the TFT, such as a drainelectrode and lines including gate lines and source lines. In the matrixdriving mode, the reliability of a dimming panel may be reduced becausethe dimming panel is exposed to backlight illumination and thereby thethreshold voltage of TFTs is shifted and off-state leakage current isgenerated. In contrast, in the segment driving mode, the firstelectrodes can be charged in a period of time corresponding to oneframe. Thus, the charging can be sufficiently achieved even when theconnection lines are made of a transparent electrode material such asindium tin oxide (ITO) or indium zinc oxide (IZO) which has lowerelectrical conductivity than the above metal material. Besides, thismethod includes no TFTs and thus can avoid a reduction in reliabilitydue to shifting of the threshold voltage of TFTs.

The connection lines may be formed of a transparent electrode materialsuch as ITO or IZO. When the connection lines are metal lines formed ofthe metal material, the dimming panel has a reduced transmittance. Inaddition, when the dimming panel is stacked above the image-providingliquid crystal panel described later, the connection lines may interferewith members of the image-providing liquid crystal panel, such as linesincluding gate lines and source lines and black matrix, which may causemoiré. In order to reduce the moiré, a diffuser is typically disposedbetween the image-providing liquid crystal panel and the dimming panel.However, use of the diffuser further reduces the transmittance of theliquid crystal display device. In contrast, use of transparentelectrodes as the connection lines can increase the transmittance of thedimming panel and can restrict the occurrence of moiré. Furthermore, thetransmittance of the liquid crystal display device can be increasedbecause no diffuser for reducing the moiré is disposed.

The planar shape of at least one island electrode may include a linearportion and may be, for example, a shape such as a quadrangle includinga rectangle, a square, and a rhombus. The planar shape of at least oneisland electrode may include a curved portion and may be, for example, ashape such as a circle or an ellipse. Furthermore, the planar shape ofat least one island electrode may have a shape formed by a combinationof a linear portion and a curved portion. The outer peripheral shape ofat least one aperture may include a linear portion and may be, forexample, a shape such as a quadrangle including a rectangle, a square,and a rhombus. The outer peripheral shape of at least one aperture mayinclude a curved portion and may be, for example, a shape such as acircle or an ellipse. Furthermore, the outer peripheral shape of atleast one aperture may have a shape formed by a combination of a linearportion and a curved portion. The planar shape of at least one islandelectrode and the outer peripheral shape of at least one aperture mayeach be designed according to the planar shape of pixels constitutingthe image-providing liquid crystal panel described later.

At least one island electrode may have an outer peripheral shapeincluding a linear portion that forms an angle of −30° to +30° withrespect to the extending direction of the linear electrodes of thesecond electrode, provided that in a view from the second substrate end,an angle formed in the clockwise direction is defined to be a negativeangle and an angle formed in the counterclockwise direction is definedto be a positive angle. When at least one of the island electrodes isdisposed in a position between adjacent two of the island electrodes ofthe base electrode of a next first electrode, adjacent first electrodesare opposed to each other with a space (gap) in between. As describedabove, the first electrodes form a fringe electric field with the linearelectrodes of the second electrode stacked above the first electrodeswith an insulating layer in between. Portions where the gaps between theadjacent first electrodes cross the linear electrodes in a plan viewtend to have an alignment defect due to insufficient movement of liquidcrystal molecules. Setting the angle formed by the linear portion andthe extending direction of the linear electrodes (hereinafter, alsoreferred to as angle θy) to −30° to +30° increases the distance betweenadjacent regions with an alignment defect (portions where the gaps crossthe linear electrodes) and thus allows dark lines to be lessrecognizable. In contrast, an angle θy of smaller than −30° or greaterthan +30° reduces the distance between adjacent regions with analignment defect and may cause dark lines to be recognizable. The angleθy is more preferably −15° to +15°. The outer periphery of the islandelectrode includes at least one linear portion described above, and mayinclude multiple linear portions. At least one of the linear portionspreferably forms an angle of −30° to +30°, more preferably an angle of−15° to +15°, with the extending direction of the linear electrodes.Preferably, a larger number of linear portions form an angle of −30° to+30°, more preferably an angle of −15° to +15°, with the extendingdirection of the linear electrodes.

Each of the first electrodes may further include a base electrodeprovided with multiple apertures, and the island electrodes may surroundthe base electrode in a plan view. Provided that one of two adjacentfirst electrodes is defined as the electrode A and the other is definedas the electrode B, formation of multiple apertures in the baseelectrode allows part of the island electrodes of the electrode A to bedisposed inside the apertures provided in the base electrode of theelectrode B. Similarly, this structure allows part of the islandelectrodes of the electrode B to be disposed inside the aperturesprovided in the base electrode of the electrode A. Also, the islandelectrodes arranged so as to surround the base electrode in a plan viewcan control the spreading of light transmitted through each dimmingunit. The base electrode may be disposed in the center of one dimmingunit, or the center of the base electrode may overlap the center of thefirst electrode. When each of the first electrodes includes a baseelectrode, the island electrodes may be arranged in a manner that theelectrode area occupancy decreases from the center of the base electrode(center of the first electrode) toward the outer periphery of the firstelectrode.

At least one island electrode of a selected electrode of two adjacentfirst electrodes may be disposed inside at least one aperture of thenext electrode. At the same time, at least one island electrode of thenext electrode may be disposed inside at least one aperture provided inthe selected electrode. Part of the island electrodes of the electrode Amay be disposed in a position inside the apertures provided in theelectrode B and in a position between the island electrodes of theelectrode B, or in a position inside the apertures provided in theelectrode B or in a position between the island electrodes of theelectrode B. Similarly, part of the island electrodes of the electrode Bmay be disposed in a position inside the apertures provided in theelectrode A and in a position between the island electrodes of theelectrode A, or in a position inside the apertures provided in theelectrode A or in a position between the island electrodes of theelectrode A.

The base electrode may be electrically connected to the lower-layerelectrode through another contact hole. Electrically connecting the baseelectrode to the lower-layer electrode allows the base electrode to beelectrically connected to at least one island electrode by thelower-layer electrode. Thereby, the base electrode and the islandelectrodes are not connected in the same plane but can be electricallyconnected by the lower-layer electrode. Thus, the same voltage can beapplied to the base electrode and the island electrodes forming onefirst electrode.

The apertures provided in the base electrode may be arranged in a mannerthat the aperture area occupancy increases from the center of the baseelectrode toward the outer periphery thereof. The aperture areaoccupancy means the proportion of the total aperture area of theapertures in a predetermined unit area in one dimming unit. Theapertures provided in the base electrode of the electrode A may bearranged in a manner that the aperture area occupancy increases from thecenter of the electrode A toward the center of the electrode B, and theapertures provided in the base electrode of the electrode B may bearranged in a manner that the aperture area occupancy increases from thecenter of the electrode B toward the center of the electrode A. Forexample, the apertures provided in the base electrode of the electrode Amay be arranged in a manner that the aperture area increases from thecenter of the electrode A toward the center of the electrode B, and theapertures provided in the base electrode of the electrode B may bearranged in a manner that the aperture area increases from the center ofthe electrode B toward the center of the electrode A. Alternatively, theapertures provided in the base electrode of the electrode A may bearranged in a manner that the number of apertures increases from thecenter of the electrode A toward the center of the electrode B, and theapertures provided in the base electrode of the electrode B may bearranged in a manner that the number of apertures increases from thecenter of the electrode B toward the center of the electrode A.

The lower-layer electrode may overlap spaces between the aperturesprovided in the base electrode of one electrode and the islandelectrodes of the next electrode in a plan view. The lower-layerelectrode may overlap a space between the electrode A and the electrodeB along the boundary therebetween. For example, the lower-layerelectrode may be formed in a cyclic shape so as to overlap a spacebetween the two electrodes along the outer periphery formed byconnecting outer apertures in the base electrode. Disposing thelower-layer electrode to overlap a space between the electrode A and theelectrode B in a plan view can change the alignment of liquid crystalmolecules in the boundary portion between the electrode A and theelectrode B and thereby can restrict the occurrence of a dark line.

The outer peripheral shape of at least one aperture (the planar shape ofthe outer periphery in a plan view) may be a quadrangle. The outerperipheral shape of at least one aperture may be any shape as long as atleast one island electrode can be disposed inside the aperture. Theouter peripheral shape of at least one aperture provided in the baseelectrode may be a rectangular shape and may be, for example, aquadrangle such as a rectangle, a square, or a rhombus. When the planarshape of at least one island electrode is a quadrangle, the outerperipheral shape of at least one aperture for having the islandelectrode(s) inside is also preferably a quadrangle in order to reducethe gap between adjacent first electrodes. A loss of the aperture ratiocan be reduced by disposing the island electrode(s) having a similarshape to the aperture(s) having the island electrode(s) inside.

An island electrode of the selected first electrode may be disposedinside an aperture in the next first electrode with a uniform peripheralspace (gap). The uniform gap width can restrict uneven appearance ofdark lines due to a gap difference. Furthermore, the loss of theaperture ratio can be minimized. The gap width may be, for example, 1 μmor greater and 20 μm or smaller.

At least one aperture may have an outer peripheral shape including alinear portion that forms an angle of −30° to +300 with respect to theextending direction of the linear electrodes of the second electrode,provided that in a view from the second substrate end, an angle formedin the clockwise direction is defined to be a negative angle and anangle formed in the counterclockwise direction is defined to be apositive angle. When at least one of the island electrodes is disposedinside at least one of the apertures provided in the base electrode of anext first electrode, setting the angle formed by the linear portion andthe extending direction of the linear electrodes (hereinafter, alsoreferred to as angle θz) to −30° to +300 increases the distance betweenadjacent regions with an alignment defect and thus allows dark lines tobe less recognizable. In contrast, an angle θz of smaller than −30° orgreater than +30° reduces the distance between adjacent regions with analignment defect and may cause dark lines to be recognizable. The angleθz is more preferably −15° to +15°. The outer periphery of the apertureincludes at least one linear portion described above, and may includemultiple linear portions. At least one of the linear portions preferablyforms an angle of −30° to +30°, more preferably an angle of −15° to+15°, with the extending direction of the linear electrodes. Preferably,a larger number of linear portions form an angle of −30° to +30°, morepreferably an angle of −15° to +15°, with the extending direction of thelinear electrodes.

The image-providing liquid crystal panel, whose structure will bedescribed later, preferably includes multiple pixels that are eachprovided with sub-pixels of multiple colors and are arranged in a matrixin a plane. The dimming units constituting the dimming panel may belarger than the pixels constituting the image-providing liquid crystalpanel. One dimming unit can dim multiple pixels.

The island electrodes may include an overlapping electrode portion thatoverlaps sub-pixels of all colors included in one pixel. The overlappingelectrode portion is an electrode portion overlapping a pixel in a planview. When a pixel includes a red sub-pixel, a green sub-pixel, and ablue sub-pixel, the overlapping electrode portion overlaps threesub-pixels of all colors including red, green, and blue. The overlappingelectrode portion may have any structure as long as it overlapssub-pixels of all colors in a plan view. For example, one islandelectrode may be provided for one pixel or for two or more adjacentpixels. Multiple island electrodes may be provided for one pixel or fortwo or more adjacent pixels. At least part of one island electrode mayoverlap sub-pixels of all colors, or multiple island electrodes may beprovided for sub-pixels of the respective colors.

In the overlapping electrode portions, the difference between themaximum value and the minimum value among electrode areas overlappingthe respective sub-pixels of the respective colors may be 30% or less ofthe maximum value. For example, the overlapping electrode portion isdisposed such that the difference between the maximum value and theminimum value among the electrode area overlapping a red sub-pixel, theelectrode area overlapping a green sub-pixel, and the electrode areaoverlapping a blue sub-pixel is 30% or less of the maximum value. Thisstructure can restrict the occurrence of color deviation that causes adesired color to be differently recognized due to unbalanced amounts oflight transmitted through sub-pixels of the respective colors in onepixel. The difference between the maximum value and the minimum valueamong the electrode areas overlapping the respective sub-pixels of therespective colors is more preferably 10% or less, still more preferably5% or less, of the maximum value. In a structure where the islandelectrodes are arranged in a manner that the electrode area decreasestoward the outer periphery of the first electrode and the sub-pixels ofmultiple colors are arranged along a first direction, adjusting theelectrode widths of the island electrodes in a second direction that isperpendicular to the first direction allows the island electrodes to bearranged in a manner that the electrode area decreases toward the outerperiphery of the first electrode and allows the difference between themaximum value and the minimum value among the electrode areasoverlapping the respective sub-pixels of the multiple colors to be 30%or less of the maximum value.

The apertures may include an overlapping aperture portion that overlapssub-pixels of all colors included in one pixel. The overlapping apertureportion is an aperture portion overlapping a pixel in a plan view. Whena pixel includes a red sub-pixel, a green sub-pixel, and a bluesub-pixel, the overlapping aperture portion overlaps three sub-pixels ofall colors including red, green, and blue. The overlapping apertureportion may have any structure as long as it overlaps sub-pixels of allcolors in a plan view. For example, one aperture may be provided for twoor more adjacent pixels, or multiple apertures may be provided for twoor more pixels. The apertures may be arranged in a manner that at leastpart of one aperture overlaps sub-pixels of all colors.

In the overlapping aperture portions, the difference between the maximumvalue and the minimum value among aperture areas overlapping therespective sub-pixels of the respective colors may be 30% or less of themaximum value. This structure can restrict the occurrence of colordeviation. The difference between the maximum value and the minimumvalue among the aperture areas overlapping the respective sub-pixels ofthe respective colors is more preferably 10% or less, still morepreferably 5% or less, of the maximum value. When the apertures arearranged in a manner that the aperture area increases toward the outerperiphery of the first electrode, adjusting the aperture widths of therespective apertures in the second direction allows the apertures to bearranged in a manner that the aperture area increases toward the outerperiphery of the first electrode and allows the difference between themaximum value and the minimum value among the aperture areas overlappingsub-pixels of the multiple colors to be 30% or less of the maximumvalue.

In the dimming panel included in the unit, boundaries between adjacentdimming units tend to be less recognizable because the luminancedistribution is smoothly changed and the occurrence of dark lines on theboundaries between dimming units can be restricted. Thus, the dimmingpanel can be also suitably used as an anti-glare panel that controls theamount of transmitting light. The anti-glare panel can be used as avehicle-mounted sun visor for vehicles such as automobiles and railwaywagons. The dimming panel has excellent viewing angle characteristicsand high transmittance, and thus can be disposed between animage-providing liquid crystal panel and a backlight and can be used asa member of a liquid crystal display device.

<Liquid Crystal Display Device>

A liquid crystal display device according to an embodiment of thepresent invention includes: an image-providing liquid crystal panel; abacklight; and a dimming unit between the image-providing liquid crystalpanel and the backlight, the dimming unit including: a dimming panel;and drive circuitry, the dimming panel sequentially including a firstsubstrate, a liquid crystal layer, and a second substrate, the firstsubstrate sequentially including an insulating substrate, a lower-layerelectrode, a first insulating layer, multiple first electrodes, a secondinsulating layer, and a second electrode which is provided with multipleparallel linear electrodes and to which a constant voltage is applied,the first electrodes including multiple island electrodes which arespaced from each other in a plan view and are electrically connected toeach other, at least one of the island electrodes being electricallyconnected to the lower-layer electrode through a contact hole, the drivecircuitry controlling voltages applied to the respective firstelectrodes.

The liquid crystal display device of the embodiment includes animage-providing liquid crystal panel, a backlight, a dimming panelbetween the image-providing liquid crystal panel and the backlight, anddrive circuitry. Disposing a dimming panel between the image-providingliquid crystal panel and the backlight can improve the contrast ratio ofthe liquid crystal display device. The liquid crystal display device ofthe embodiment can smooth the change in gray scale distribution betweenadjacent dimming units as described later. Furthermore, the amount ofbacklight illumination transmitted can be controlled in smaller areasthan by local dimming with the backlight, and thus occurrence of a halophenomenon can be restricted.

The image-providing liquid crystal panel may be any liquid crystalpanel, and an example thereof is a liquid crystal panel sequentiallyincluding an active matrix substrate, a liquid crystal layer, and acolor filter substrate. The image-providing liquid crystal panel may bea horizontally aligned liquid crystal panel such as a fringe fieldswitching (FFS) liquid crystal panel or an in-plane switching (IPS)liquid crystal panel in terms of excellent viewing anglecharacteristics.

The active matrix substrate includes, for example, on an insulatingsubstrate, parallel gate lines and parallel source lines extending in adirection crossing the gate lines with an insulating film in between,and, as switching elements, thin film transistors (TFTs) at theintersections of the gate lines and the source lines. A regionsurrounded by two adjacent gate lines and two adjacent source lines isherein referred to as a sub-pixel. The active matrix substrate includesmultiple sub-pixel electrodes provided for the respective sub-pixels andeach connected to the corresponding TFT via the corresponding drainelectrode. In a horizontally aligned liquid crystal panel, the activematrix substrate further includes a common electrode stacked above thesub-pixel electrodes with an insulating layer in between.

The liquid crystal layer contains liquid crystal molecules. The liquidcrystal molecules may have a positive anisotropy of dielectric constant(As) (positive type) or a negative anisotropy of dielectric constant(negative type) defined by the following formula.

Δε=(dielectric constant in major axis direction of liquid crystalmolecules)−(dielectric constant in minor axis direction of liquidcrystal molecules)  (L)

The color filter substrate includes, for example, on an insulatingsubstrate, color filters of multiple colors and a black matrixpartitioning the color filters of the respective colors in a plan view.The color filters of multiple colors may include red color filters,green color filters, and blue color filters. The color filters ofmultiple colors overlap the sub-pixels in a plan view.

The image-providing liquid crystal panel preferably includes multiplepixels that are each provided with sub-pixels of multiple colors and arearranged in a matrix in a plane. The sub-pixels of multiple colors meansub-pixels overlapping the color filters of multiple colors. In colorfilters of multiple colors including red color filters, green colorfilters, and blue color filters, for example, a sub-pixel overlapping ared color filter is also referred to as a red sub-pixel, a sub-pixeloverlapping a green color filter is also referred to as a greensub-pixel, and a sub-pixel overlapping a blue color filter is alsoreferred to as a blue sub-pixel.

The image-providing liquid crystal panel may be sandwiched by a pair ofpolarizers. The polarizers may be linear polarizers and may be arrangedwith their absorption axes being perpendicular to each other, forexample.

The backlight may be any backlight conventionally known in the field ofliquid crystal display devices, and examples thereof include edgebacklights and direct backlights. Driving a direct backlight by localdimming allows the liquid crystal display device to attain an effect offurther improving the contrast ratio.

Hereinafter, the present invention is specifically described withreference to examples and drawings. The examples, however, are notintended to limit the present invention.

Example 1

FIG. 1 is an exploded perspective view of a liquid crystal displaydevice of Example 1. As shown in FIG. 1, the liquid crystal displaydevice of Example 1 includes an image-providing liquid crystal panel 1,a backlight 3, a dimming panel 2 between the image-providing liquidcrystal panel 1 and the backlight 3, and drive circuitry 50. A pair ofpolarizers may be disposed on the surfaces of the image-providing liquidcrystal panel 1 and on the surfaces of the dimming panel 2. As shown inFIG. 1, a first polarizer 4, the image-providing liquid crystal panel 1,a second polarizer 5, the dimming panel 2, and a third polarizer 6 maybe disposed in this order. The image-providing liquid crystal panel 1and the dimming panel 2 may share the second polarizer 5 disposedtherebetween. The first polarizer 4 and the second polarizer 5 arearranged with their absorption axes being perpendicular to each other.The second polarizer 5 and the third polarizer 6 are arranged with theirabsorption axes being perpendicular to each other. The first polarizer4, the second polarizer 5, and the third polarizer 6 are each anabsorptive linear polarizer. Between the third polarizer 6 and thebacklight 3 may be disposed an optical sheet 7 for diffusing lightemitted from the backlight, such as a diffuser.

The image-providing liquid crystal panel 1 may be an active matrixliquid crystal panel. The image-providing liquid crystal panel 1 mayinclude, for example, red, green, and blue sub-pixels, and threesub-pixels of the three colors may constitute one pixel. Multiple pixelsare arranged in a matrix in an in-plane direction of the image-providingliquid crystal panel 1. The backlight 3 may be any backlightconventionally known in the field of liquid crystal display devices, andis preferably a direct backlight because local dimming driving canprovide an effect of further improving the contrast ratio.

Hereinafter, the dimming panel used in Example 1 is described. FIG. 2 isa schematic cross-sectional view showing a part of the dimming panelused in Example 1. FIG. 3 is a schematic plan view showing one of firstelectrodes used in the dimming panel of Example 1. FIG. 4 is a schematicplan view showing a part of the dimming panel used in Example 1. FIG. 2is a schematic cross-sectional view taken along the line X1-X2 in FIG.4.

As shown in FIG. 2, the dimming panel 2 sequentially includes a firstsubstrate 10, a liquid crystal layer 30, and a second substrate 40. Thedimming panel 2 is a horizontally aligned dimming panel, and the firstsubstrate 10 sequentially includes an insulating substrate 11, alower-layer electrode 12, a first insulating layer 13, multiple firstelectrodes including 14A and 14B, a second insulating layer 15, and asecond electrode 16. The first electrodes 14A and 14B and the secondelectrode 16 may each be formed of, for example, a transparent electrodematerial such as ITO or IZO. The first insulating layer 13 may be anylayer that can insulate the lower-layer electrode 12 from the firstelectrodes 14A and 14B. The second insulating layer 15 may be any layerthat can insulate the first electrodes 14A and 14B from the secondelectrode 16. The first insulating layer 13 and the second insulatinglayer 15 may be formed from a silicon oxide film, a silicon nitridefilm, or the like.

As shown in FIG. 2, island electrodes 14Ab are electrically connected toeach other by the lower-layer electrodes 12 through contact holes CH2penetrating the second insulating layer 15. A base electrode 14Aa iselectrically connected to the lower-layer electrode 12 through a contacthole CH3 penetrating the second insulating layer 15. In other words, atleast one island electrode 14Ab and the base electrode 14Aa areelectrically connected by the lower-layer electrode 12. The firstelectrode 14A (in FIG. 2, the base electrode 14Aa) is electricallyconnected to one of multiple connection lines 19 disposed between theinsulating substrate 11 and a third insulating layer 17 through acontact hole CH1 penetrating the second insulating layer 15 and thethird insulating layer 17 on the insulating substrate 11 end. The liquidcrystal display device of Example 1 includes drive circuitry thatcontrols the voltages applied to the respective first electrodes 14. Thefirst electrodes 14 are each connected to the drive circuitry via thecorresponding connection line 19. In the contact hole CH1, thelower-layer electrode 12 may be disposed in a portion for connecting thefirst electrode 14A and the connection line 19. Between the insulatingsubstrate 11 and the lower-layer electrode 12 may be disposed a fourthinsulating layer 20. FIG. 2 shows a case where the base electrode 14Aais electrically connected to the connection line 19 through the contacthole CH1. Alternatively, at least one island electrode may beelectrically connected to the connection line 19 through the contacthole CH1.

Hereinafter, the structure of the first electrodes used in the dimmingpanel of Example 1 is described with reference to FIG. 3. As shown inFIG. 3, in one first electrode 14 (14A), multiple island electrodes 14 b(14Ab) are arranged with intervals in a plan view. The island electrodes14 b are arranged in a manner that the electrode area concentricallydecreases from the center of a base electrode 14 a (14Aa) toward theouter periphery of the first electrode 14. In FIG. 3 and thelater-described FIG. 4, the portions surrounded by two-dot chain linesindicate positioning areas for roughly locating the base electrodes 14 awhen the first electrodes 14 are arranged in a plane of the dimmingpanel. The outer peripheral shape of the positioning area may bedifferent from the outer peripheral shape of the base electrode 14 a.The base electrode 14 a is provided with multiple apertures 14 c (14Ac).The apertures 14 c are arranged in a manner that the aperture areaconcentrically increases from the center of the base electrode 14 a(14Aa) toward the outer periphery of the first electrode 14A. In Example1, the planar shape of at least one island electrode 14 b is aquadrangle, and the outer peripheral shape of at least one aperture 14 cis also a quadrangle.

The outer peripheral shape of the positioning area is preferably a shapethat allows tidy arrangement of a plurality of the shapes on a flatsurface. The outer peripheral shape of the positioning area may be ashape such as a triangle, a quadrangle, or a hexagon. Examples of thetriangle include equilateral triangles, isosceles triangles, and righttriangles. Examples of the quadrangle include squares, rectangles, andrhombuses. In order to achieve a smoother change in luminancedistribution, the outer peripheral shape of the positioning area ispreferably a regular polygon, and an equilateral triangle, a square, aregular hexagon, or the like is suitable.

In Example 1, the outer peripheral shape of the positioning area is ahexagon. Thus, one first electrode 14A is adjacent to six other firstelectrodes with its six sides as boundaries. The arrangement of threefirst electrodes 14B, 14C, and 14D among the six first electrodesadjacent to the first electrode 14A is described with reference to FIG.4. As shown in FIG. 4, the first electrodes 14B, 14C, and 14Drespectively include the base electrodes 14Ba, 14Ca, and 14Da andmultiple island electrodes 14Bb, 14Cb, and 14Db respectively surroundingthe base electrodes 14Ba, 14Ca, and 14Da in a plan view. The baseelectrodes 14Ba, 14Ca, and 14Da are respectively provided with multipleapertures 14Bc, 14Cc, and 14Dc.

Here, two adjacent first electrodes 14A and 14B are focused on. As shownin FIG. 2 and FIG. 4, at least one island electrode 14Ab of the firstelectrode 14A is disposed in at least one position selected from thegroup consisting of a position inside at least one aperture 14Bc in thebase electrode 14Ba and a position between adjacent two of the islandelectrodes 14Bb of the first electrode 14B. Also, at least one islandelectrode 14Bb of the first electrode 14B is disposed in at least oneposition selected from the group consisting of a position inside atleast one aperture 14Ac in the base electrode 14Aa and a positionbetween adjacent two of the island electrodes 14Ab of the firstelectrode 14A.

FIG. 5A is a partially enlarged schematic plan view showing an exampleof the island electrodes shown in FIG. 3. FIG. 5B is a partiallyenlarged schematic plan view showing another example of the islandelectrodes shown in FIG. 3. FIG. 5A and FIG. 5B are each a partiallyenlarged schematic plan view showing a part of the island electrodessurrounded by a one-dot chain line in FIG. 3. In FIG. 5A and FIG. 5B,the lower-layer electrodes 12 disposed in a layer below the islandelectrodes 14Ab are shown by dotted lines, and contact holes CH2connecting the island electrodes 14Ab and the lower-layer electrodes 12are shown by white squares. The lower-layer electrode 12 may overlap theboundaries of the pixels 9 constituting the image-providing liquidcrystal panel 1. For example, the island electrodes 14Ab may beconnected in the line direction and column direction by the lower-layerelectrode 12 disposed in a mesh pattern that overlaps the boundariesbetween the pixels as shown in FIG. 5A, or may be connected in adiagonal direction by the lower-layer electrode 12 that is disposed inthe diagonal direction and overlaps the boundaries between the pixels asshown in FIG. 5B.

Hereinafter, a method for arranging the first electrodes 14 is describedwith reference to FIG. 6. FIG. 6 is a plan view showing an arrangementexample of first electrodes with reference to pixels of animage-providing liquid crystal panel. In FIG. 6, the portions surroundedby two-dot chain lines are positioning areas for roughly locating thebase electrodes 14 a. The base electrodes 14 a and the island electrodes14 b of the first electrodes 14 in the dimming panel 2 may be arrangedwith reference to the pixels of the image-providing liquid crystalpanel. As shown in FIG. 6, multiple positioning areas are designed to betidily arranged in a plane of the dimming panel. The base electrodes 14a are positioned with reference to the positioning areas. In FIG. 6, theouter peripheral shape of each positioning area is a hexagon. The baseelectrodes 14Aa, 14Ba, 14Ca, and 14 Da are positioned with reference tothe hexagonal positioning areas tidily arranged in the plane. The islandelectrodes 14 b may be concentrically arranged from the center of eachfirst electrode 14.

Hereinafter, the arrangement of the island electrodes is described withreference to FIG. 7 to FIG. 9. FIG. 7 is a schematic view for describinga manner for reducing the electrode area of the island electrodes inExample 1. As shown in FIG. 7, the areas of the island electrodes 14Aboverlapping pixels 9 of the image-providing liquid crystal panel are setin 16 grades, for example. Provided that the electrode area of anelectrode portion overlapping the entire surface of one pixel 9 isdefined as 100%, the areas of electrode portions overlapping therespective pixels 9 (overlapping electrode portions) gradually decrease,such as 93.3%, 86.7%, and go on, from the center of the first electrode14A toward the outer periphery of the first electrode 14A.

FIG. 8 is a schematic plan view showing an example of disposing anoverlapping electrode portion with reference to one pixel in Example 1.FIG. 9 is a schematic plan view showing a preferred example of disposingan overlapping electrode portion with reference to one pixel inExample 1. FIG. 8 and FIG. 9 each show a case where the electrode areaof an island electrode overlapping one pixel 9 (overlapping electrodeportion) is 13.3%. The overlapping electrode portions are preferablydisposed in a manner that no color deviation is caused when the dimmingpanel 2 is stacked above the image-providing liquid crystal panel 1. Asshown in FIG. 8, the pixel 9 includes a red sub-pixel 8R, a greensub-pixel 8G, and a blue sub-pixel 8B. Here, when the island electrode14Ab (overlapping electrode portion) overlaps the blue sub-pixel 8Bonly, for example, the amount of light transmitted through the bluesub-pixel 8B is smaller than the amount of light transmitted through thered sub-pixel 8R and the green sub-pixel 8G, which may result in colordeviation causing a failure in providing a desired color. Accordingly,the overlapping electrode portion preferably overlaps all of the redsub-pixel 8R, the green sub-pixel 8G, and the blue sub-pixel 8B includedin the pixel 9 as shown in FIG. 9. More preferably, the differencebetween the maximum value and the minimum value among the electrodeareas overlapping the respective sub-pixels of the respective colors is30% or less of the maximum value.

Provided that the red sub-pixel 8R, the green sub-pixel 8G, and the bluesub-pixel 8B are aligned in a direction D1, adjusting the electrodewidth in a direction D2 that is perpendicular to the direction D1 allowsthe difference between the maximum value and the minimum value among theelectrode areas overlapping the red sub-pixel 8R, the green sub-pixel8G, and the blue sub-pixel 8B to be 30% or less of the maximum value andallows control of the electrode areas toward the outer periphery offirst electrode 14A.

FIG. 9 describes the structure where one island electrode is disposedfor one pixel. Still, one island electrode 14Ab may be disposed for onepixel, or one island electrode 14Ab may be disposed for two pixelsadjacent in the D2 direction. As described later, in order to allow darklines to be less recognizable when one aperture 14Ac is provided for twopixels adjacent in the D2 direction, one island electrode 14Ab ispreferably disposed for two pixels adjacent in the D2 direction.

Hereinafter, the arrangement of multiple overlapping aperture portionsprovided in the base electrodes is described with reference to FIG. 10and FIG. 11. FIG. 10 is a schematic plan view showing an example ofdisposing an overlapping aperture portion for each pixel in Example 1.FIG. 11 is a schematic plan view showing a preferred example ofdisposing an overlapping aperture portion for each pixel in Example 1.FIG. 10 and FIG. 11 are each a partially enlarged schematic plan viewshowing a part surrounded by a dotted line of the base electrode in FIG.3. The numbers (%) shown in FIG. 10 and FIG. 11 each indicate theproportion of the electrode area overlapping one pixel 9 (overlappingelectrode portion) relative to the area of the pixel 9 defined as 100%.The proportion of the area of an aperture overlapping the pixel 9(overlapping aperture portion) may be appropriately set in considerationof the width (gap width) between two adjacent first electrodes.Accordingly, as the electrode area overlapping one pixel 9 decreasesfrom the center of the base electrode toward the outer periphery, theaperture area overlapping the corresponding pixel 9 increases. As shownin FIG. 9, when one pixel 9 includes a red sub-pixel 8R, a greensub-pixel 8G, and a blue sub-pixel 8B, the overlapping aperture portionpreferably overlaps all of the red sub-pixel 8R, the green sub-pixel 8G,and the blue sub-pixel 8B similarly to the above-mentioned case of theoverlapping electrode portion. The difference between the maximum valueand the minimum value among the aperture areas overlapping therespective sub-pixels of the respective colors is preferably 30% or lessof the maximum value.

Although not shown in FIG. 10 and FIG. 11, in the aperture 14Ac may bedisposed the island electrode 14Bb of the next first electrode 14B, forexample. In the boundary portion between the first electrode 14A and thefirst electrode 14B, a dark line tends to appear due to an alignmentdefect of liquid crystal molecules. Thus, when multiple overlappingaperture portions (apertures 14Ac) are aligned in the line direction ofthe pixels 9 as shown in FIG. 10, dark lines tend to be recognized alongthe line direction. In contrast, as shown in FIG. 11, when one aperture14Ac is disposed for two pixels adjacent in the D2 direction and theoverlapping aperture portions are scattered without being aligned in aspecific direction, dark lines can be less recognizable. Collecting theapertures 14Ac or the island electrodes 14Bb as shown in FIG. 11 canreduce the number of apertures on the boundary portions between thefirst electrode 14A and the first electrode 14B and thereby can reduceportions that could cause dark lines due to an alignment defect ofliquid crystal molecules.

Hereinafter, the second electrode 16 is described with reference to FIG.12. FIG. 12 is a schematic plan view of the second electrode shown inFIG. 2. As shown in FIG. 12, the second electrode 16 includes parallellinear electrodes 16 a. Slits 16 b are provided between the linearelectrodes 16 a. The second electrode 16 may be disposed on the dimmingpanel 2 entirely. Although not being shown, the linear electrodes 16 amay be electrically connected to each other by, for example, anelectrode connecting portion disposed at the terminals of the linearelectrodes 16 a. The second electrode 16 is connected to, for example, acommon line disposed on the periphery of the dimming panel, and aconstant voltage is applied thereto. In Example 1, an extendingdirection D3 of the linear electrodes 16 a is set to be 80° in thecounterclockwise direction with respect to the absorption axis of thefirst polarizer 4 or the absorption axis of the second polarizer 5defined to be 0° in a view seen from the second substrate 40 end. Inother words, an angle θx formed by the direction D3 and one of theabsorption axis of the first polarizer 4 and the absorption axis of thesecond polarizer 5 is set to 80°.

As shown in FIG. 2, the liquid crystal layer 30 is sandwiched betweenthe first substrate 10 and the second substrate 40 while having apredetermined thickness maintained with spacers 31. The liquid crystallayer 30 may contain liquid crystal molecules whose anisotropy ofdielectric constant (As) has a positive value or a negative value. Theinsulating substrate 11 and the second substrate 40 are supportsubstrates sandwiching the liquid crystal layer 30 and may each be aninsulating substrate such as a glass plate or a plastic plate such as apolycarbonate plate. An alignment film defining the initial alignmentazimuth of the liquid crystal molecules may be disposed between thefirst substrate 10 and the liquid crystal layer 30 and between thesecond substrate 40 and the liquid crystal layer 30.

FIG. 13 is a schematic plan view of the dimming panel, showing anexample of a method for driving the first electrodes in Example 1. InFIG. 13, positioning areas for locating the base electrodes 14 a areshown by two-dot chain lines. As shown in FIG. 13, the outer peripheralshape of each positioning area is a hexagon, and the first electrodes 14(base electrodes 14 a) are arranged in the line direction and the columndirection in a plane of the dimming panel 2. The first electrodes 14 mayeach be connected to drive circuitry 50 via the corresponding connectionline 19. A driving method in which each of the first electrodes 14 isdirectly connected to the drive circuitry 50 is referred to as a segmentmode. The connection lines 19 formed from a transparent electrode suchas ITO can increase the transmittance of the dimming panel 2. As shownin FIG. 13, the first electrodes 14 arranged in the column direction maybe arranged in a manner that the contact holes CH1 are shifted in theline direction. The drive circuitry 50 may be disposed in a frame regionthat is outside the dimming region where multiple dimming units arearranged.

FIG. 14 is a schematic graph showing a change in luminance distributionof the dimming panel used in the liquid crystal display device ofExample 1. FIG. 14 schematically shows the change in luminance between acenter Y1 of the first electrode 14A and a center Y2 of the firstelectrode 14B shown in FIG. 4. FIG. 14 shows that the luminance smoothlychanges between the adjacent first electrodes in Example 1.

As described above, in Example 1, one first electrode 14A is adjacent tosix other first electrodes. Also, the first electrodes each include theisland electrodes 14 b electrically connected to each other by thelower-layer electrodes 12. As shown in FIG. 4, at least one islandelectrode 14Ab of the first electrode 14A is disposed inside at leastone aperture in the base electrode of each of the six other firstelectrodes or between the island electrodes of each of the six otherfirst electrodes. Also, at least one island electrode of each of the sixother first electrodes is disposed inside at least one aperture 14 c inthe base electrode 14 a of the first electrode 14A or between the islandelectrodes 14 b of the first electrode 14A. In Example 1, the change inluminance distribution can be smoothed between one first electrode andthe next first electrode in six directions. Thus, the boundaries betweendimming units can be less recognizable than in the later-described caseswhere the outer peripheral shape of the positioning areas is aquadrangle. Meanwhile, the hexagonal outer peripheral shape of thepositioning areas complicates the relation with the corresponding pixelsconstituting the image-providing liquid crystal panel.

Example 2

Hereinafter, a liquid crystal display device of Example 2 is describedwith reference to FIG. 15 to FIG. 18. The liquid crystal display deviceof Example 2 has the same structure as that of Example 1 except for thestructure of the first electrodes used in the dimming panel. Thedescription for the structures similar to the liquid crystal displaydevice of Example 1 is omitted here. FIG. 15 is a schematic plan viewshowing one of first electrodes used in a dimming panel of Example 2.FIG. 16 is a plan view of the first electrodes arranged with referenceto the pixels of the image-providing liquid crystal panel. FIG. 17 is aschematic plan view showing an arrangement example of first electrodesshown in FIG. 15. FIG. 18 is a schematic plan view of the dimming panelin Example 2, showing an example of a method for driving the firstelectrodes. In FIG. 15 and FIG. 17, the portions surrounded by two-dotchain lines are positioning areas for locating the first electrodes. InFIG. 18, positioning areas for locating base electrodes 114 a areindicated by two-dot chain lines.

As shown in FIG. 15, the outer peripheral shape of the positioning areasfor locating the first electrodes in Example 2 is a quadrangle (square).Each base electrode 114 a is provided with multiple apertures 114 c(114Ac). Multiple island electrodes 114 b (114Ab) surround the baseelectrode 114 a in a plan view. The island electrodes 114 b are arrangedin a manner that the electrode area decreases from the center of thebase electrode 114 a toward the outer periphery of the first electrode114. The apertures 114 c are arranged in a manner that the aperture areaincreases from the center of the base electrode 114 a toward the outerperiphery of the first electrode 114. In Example 2, the planar shape ofat least one island electrode 114 b is a quadrangle, and the outerperipheral shape of at least one aperture 114 c is also a quadrangle.

As shown in FIG. 16, base electrodes 114Aa, 114Ba, 114Ca, and 114Da aretidily arranged on a flat surface. The island electrodes 114Ab arearranged to form concentric squares from the center of the baseelectrode 114Aa toward the outer periphery of the first electrode 114A.

In Example 2, the outer peripheral shape of the positioning areas is aquadrangle. Thus, one first electrode 114A is adjacent to four otherfirst electrodes with its four sides as boundaries. The arrangement oftwo first electrodes 114B and 114D among the four other first electrodesadjacent to the first electrode 114A and the first electrode 114Cdiagonal to the first electrode 114A is described with reference to FIG.17. As shown in FIG. 17, the first electrodes 114A, 114B, 114C, and 114Drespectively include the base electrodes 114Aa, 114Ba, 114Ca, and 114Daand multiple island electrodes 114Ab, 114Bb, 114Cb, and 114Dbrespectively surround the base electrodes 114Aa, 114Ba, 114Ca, and 114Dain a plan view. In FIG. 17, the portions surrounded by two-dot chainlines are base electrodes. The base electrodes 114Aa, 114Ba, 114Ca, and114Da are respectively provided with multiple apertures 114Ac, 114Bc,114Cc, and 114Dc.

In Example 2, the first electrodes 114 each include the islandelectrodes 114 b electrically connected to each other by the lower-layerelectrodes 12. Thus, as shown in FIG. 17, at least one island electrode114Ab of the first electrode 114A is disposed inside at least oneaperture 114Bc provided in the base electrode 114Ba of the firstelectrode 114B that is adjacent to the first electrode 114A in theup/down direction, and at least one island electrode 114Ab is disposedinside at least one aperture 114Dc provided in the base electrode 114Daof the first electrode 114D that is adjacent to the first electrode 114Ain the left/right direction. Also, at least one island electrode 114Bbof the first electrode 114B is disposed inside at least one aperture114Ac provided in the base electrode 114Aa of the first electrode 114A,and at least one island electrode 114Db of the first electrode 114D isdisposed inside at least one aperture 114Ac provided in the baseelectrode 114Aa of the first electrode 114A. Meanwhile, in the firstelectrode 114A and the first electrode 114C diagonally adjacent to thefirst electrode 114A, no island electrode of one first electrode isdisposed inside of least one aperture provided in the base electrodeand/or between the island electrodes of the other first electrode.

As shown in FIG. 18, the outer peripheral shape of the positioning areasis a quadrangle, and the first electrodes 114 (base electrodes 114 a)are arranged in the line direction and in the column direction in aplane of the dimming panel 2. The first electrodes 114 may each beconnected to the drive circuitry 50 via the corresponding connectionline 19.

The dimming panel of Example 2 also succeeded in smoothing the change inluminance distribution between adjacent dimming units. In Example 2, theouter peripheral shape of the positioning areas is a quadrangle. Thus,the change in luminance distribution can be smoothed between one firstelectrode 114A and four adjacent first electrodes in the up and downdirections and the left and right directions. In addition, thequadrangular outer peripheral shape of the positioning areas cansimplify the relation with the corresponding pixels constituting theimage-providing liquid crystal panel and can achieve an easy design.Meanwhile, the change in luminance distribution in the diagonaldirections is more smoothed in Example 1 than in Example 2.

Example 3

Hereinafter, a liquid crystal display device of Example 3 is describedwith reference to FIG. 19 to FIG. 25 and FIG. 27A to FIG. 27C. Theliquid crystal display device of Example 3 has the same structure asthat of Example 1 except for the structure of the first electrodes usedin the dimming panel. The description for the structures similar to theliquid crystal display device of Example 1 is omitted here. FIG. 19 is aschematic plan view showing one of first electrodes used in a dimmingpanel of Example 3. FIG. 20 is a partially enlarged schematic plan viewshowing an example of the island electrodes shown in FIG. 19. FIG. 20 isan enlarged schematic plan view showing a part of the island electrodessurrounded by one-dot chain lines shown in FIG. 19. FIG. 21 is aschematic plan view showing an arrangement example of first electrodesshown in FIG. 19. In FIG. 19 and FIG. 21, the portions surrounded bytwo-dot chain lines are base electrodes.

As shown in FIG. 19, the outer peripheral shape of the positioning areasfor locating the first electrodes in Example 3 is a quadrangle (square).Each base electrode 214 a is provided with multiple apertures 214 c(214Ac). Multiple island electrodes 214 b (214Ab) surround the baseelectrode 214 a in a plan view. The island electrodes 214 b are arrangedin a manner that the electrode area decreases from the center of thebase electrode 214 a toward the outer periphery of the first electrode214. The apertures 214 c are arranged in a manner that the aperture areaincreases from the center of the base electrode 214 a toward the outerperiphery of the first electrode 214.

In FIG. 20, the lower-layer electrode 12 disposed in a layer below theisland electrodes 214Ab is shown by dotted lines, and contact holes CH2connecting the island electrodes 214Ab and the lower-layer electrode 12are shown by white squares. For example, as shown in FIG. 20, threeisland electrodes 214Ab aligned in the line direction may be connectedto each other by the lower-layer electrode 12 and diagonally arrangedisland electrodes 214Ab may also be connected to each other by thelower-layer electrode 12.

Similarly to Example 2, the outer peripheral shape of the positioningareas is a quadrangle in Example 3. Thus, one first electrode 214A isadjacent to four other first electrodes with its four sides asboundaries. Also, the first electrodes 214 each include the islandelectrodes 214 b electrically connected to each other by the lower-layerelectrodes 12. Thus, as shown in FIG. 21, at least one island electrode214Ab of the first electrode 214A is disposed inside at least oneaperture 214Bc provided in a base electrode 214Ba of a first electrode214B and inside at least one aperture 214Dc provided in a base electrode214Da of a first electrode 214D, the first electrodes 214B and 214Dbeing adjacent to the first electrode 214A respectively in the up/downdirection and in the left/right direction with one of the fourperipheral sides of the base electrode 114Aa as a boundary. Also, atleast one island electrode 214Bb of the first electrode 214B is disposedinside at least one aperture 214Ac provided in the base electrode 214Aaof the first electrode 214A, and at least one island electrode 214Db ofthe first electrode 214D is disposed inside at least one aperture 214Acprovided in the base electrode 214Aa of the first electrode 214A.Meanwhile, in the first electrode 214A and the first electrode 214Cdiagonally adjacent to the first electrode 214A, no island electrode ofone first electrode is disposed inside at least one aperture provided inthe base electrode and/or between the island electrodes of the otherfirst electrode.

In the first electrodes 214 used in Example 3, the planar shape of theisland electrodes 214 b and the outer peripheral shape of the apertures214 c are different from those of the first electrodes 114 used inExample 2. As shown in FIG. 19, in Example 3, at least one islandelectrode 214 b has an outer peripheral shape including linear portions,and at least one of the liner portions forms an angle of −30° to +30°with the extending direction D3 of the linear electrodes 16 a of thesecond electrode 16. Also, at least one aperture 214 c has an outerperipheral shape including a linear portion that forms an angle of −30°to +30° with the extending direction D3 of the linear electrodes 16 a ofthe second electrode 16.

FIG. 22 is a schematic view for describing a manner for reducing theelectrode area of the island electrodes in Example 3. As shown in FIG.22, the areas of the island electrodes 214Ab overlapping the pixels 9 ofthe image-providing liquid crystal panel are set in 16 grades, forexample. Provided that the electrode area of an electrode portionoverlapping the entire surface of one pixel 9 is defined as 100%, theelectrode areas overlapping the respective pixels 9 gradually decrease,such as 93.3%, 86.7%, and go on, from the center of the first electrode214A toward the outer periphery of the first electrode 214A.

FIG. 23 is a schematic plan view showing an example of disposing anisland electrode with reference to one pixel in Example 3. FIG. 24 is aschematic plan view showing a preferred example of disposing islandelectrodes with reference to one pixel in Example 3. FIG. 23 and FIG. 24each show a case where the electrode area of island electrode(s)overlapping one pixel 9 (overlapping electrode portion) is 13.3%. Theoverlapping electrode portion is preferably disposed in a manner that nocolor deviation is caused when the dimming panel 2 is stacked above theimage-providing liquid crystal panel 1. As shown in FIG. 23, the pixel 9includes a red sub-pixel 8R, a green sub-pixel 8G, and a blue sub-pixel8B. Here, when one island electrode 214Ab (overlapping electrodeportion) overlaps the green sub-pixel 8G only, for example, the amountof light transmitted through the green sub-pixel 8G is smaller than theamount of light transmitted through the red sub-pixel 8R and the bluesub-pixel 8B, which may result in color deviation causing a failure inproviding a desired color. Accordingly, as shown in FIG. 24, threeisland electrodes 214Ab are preferably disposed for one pixel 9, and thedifference between the maximum value and the minimum value among theelectrode area overlapping the red sub-pixel 8R, the electrode areaoverlapping the green sub-pixel 8G, and the electrode area overlappingthe blue sub-pixel 8B is preferably 30% or less of the maximum value.Provided that the red sub-pixel 8R, the green sub-pixel 8G, and the bluesub-pixel 8B are aligned in the direction D1, adjusting the electrodewidths of the three island electrodes in the direction D2 that isperpendicular to the direction D1 allows control of the electrode areas.

FIG. 25 is a schematic plan view showing an example of disposingapertures in the base electrodes in Example 3. FIG. 26 is a schematicplan view showing a preferred example of arranging apertures in the baseelectrodes in Example 3. The numbers (%) shown in FIG. 25 and FIG. 26each indicate the proportion of the electrode area overlapping one pixel9 (overlapping electrode portion) relative to the area of the pixel 9defined as 100%. The proportion of the area of an aperture overlappingthe pixel 9 (overlapping aperture portion) may be appropriately set inconsideration of the width (gap width) between two adjacent firstelectrodes. Accordingly, as the electrode area overlapping one pixel 9decreases from the center of the base electrode toward the outerperiphery, the aperture area overlapping the corresponding pixel 9increases. When multiple apertures 214Ac (overlapping aperture portions)are aligned in the line direction of the pixels 9 as shown in FIG. 25,dark lines tend to be recognized along the line direction. In contrast,in FIG. 26, two apertures 214Ac adjacent to each other in the D2direction shown in FIG. 25 are opposed to each other to form oneaperture 214Ac. Thereby, the overlapping aperture portions are scatteredwithout being aligned in a specific direction, and thus dark lines canbe less recognizable. Collecting the apertures 214Ac or the islandelectrodes 214Bb as shown in FIG. 26 can reduce the number of apertureson the boundary portions between the first electrodes and thereby canreduce portions that could cause dark lines due to an alignment defectof liquid crystal molecules.

The occurrence of dark lines is described with reference to FIGS. 27A to27C. FIG. 27A is an enlarged schematic plan view of a boundary portionbetween adjacent first electrodes shown in FIG. 21. FIG. 27B is anenlarged schematic view for describing an island electrode shown in FIG.27A. FIG. 27C is an enlarged schematic view for describing an apertureshown in FIG. 27A. FIG. 27A shows an enlarged view of a portion wherethe island electrodes 214Ab of the first electrode 214A are disposedinside the apertures 214Bc provided in the base electrode 214Ba of thefirst electrode 214B. Similarly to Example 1, the extending direction D3of the linear electrodes 16 a of the second electrode 16 in Example 3 isset to form an angle θx of 80° with one of the absorption axis of thefirst polarizer 4 and the absorption axis of the second polarizer 5.

As shown in FIG. 27B, at least one island electrode 214Ab has an outerperiphery including, for example, four linear portions 214Ab₁, 214Ab₂,214Ab₃, and 214Ab₄. Provided that in a view from the second substrate 40end, an angle formed in the clockwise direction with respect to thedirection D3 is defined to be a negative angle and an angle formed inthe counterclockwise direction therewith is defined to be a positiveangle and the direction D3 forms angles θ_(y1), θ_(y2), θ_(y3), andθ_(y4) with the linear portions 214Ab₁, 214Ab₂, 214Ab₃, and 214Ab₄,respectively, at least one angle of θ_(y1), θ_(y2), θ_(y3), or θ_(y4) ispreferably −30° to +30°, more preferably −15° to +15°. All of the anglesθ_(y1), θ_(y2), θ_(y3), and θ_(y4) may be −30° to +300 or −15° to +15°.

As shown in FIG. 27C, similarly to the island electrodes, the firstelectrode 214B adjacent to the first electrode 214A includes at leastone aperture 214Bc having an outer periphery including, for example,four linear portions 214Bc₁, 214Bc₂, 214Bc₃, and 214Bc₄ in the baseelectrode 214Ba. Provided that the direction D3 forms angles θz₁, θz₂,θz₃, and θz₄ with the linear portions 214Bc₁, 214Bc₂, 214Bc₃, and214Bc₄, respectively, at least one angle of θ_(z1), θ_(z2), θ_(z3), orθ_(z4) is preferably −30° to +30°, more preferably −15° to +15°. All ofthe angles θ_(z1), θ_(z2), θ_(z3), and θ_(z4) may be −30° to +30° or−15° to +15°.

In FIG. 25, one aperture 214Ac has a triangle outer peripheral shapeincluding three linear portions, whose two linear portions each form anangle of −30° to +30° with the direction D3. Meanwhile, in FIG. 26, oneaperture 214Ac has a parallelogram-like outer peripheral shape includingfour linear portions. All the four linear portions form an angle of −30°to +30° with the direction D3. Thus, the occurrence of dark linesbetween adjacent first electrodes can be more restricted in the case ofarranging apertures as in FIG. 26 than in the case of arrangingapertures as in FIG. 25.

The dimming panel of Example 3 also succeeded in smoothing the change inluminance distribution between adjacent dimming units. Similarly toExample 2, the quadrangular outer peripheral shape of the positioningareas for locating the first electrodes in Example 3 can simplify therelation with the corresponding pixels constituting the image-providingliquid crystal panel and can achieve an easy design. Furthermore, theplanar shape of the island electrodes and the outer peripheral shape ofthe apertures provided in the base electrodes each include multiplelinear portions, and at least one linear portion forms a predeterminedangle with the extending direction of the linear electrodes of thesecond electrode. Thus, the occurrence of dark lines between adjacentfirst electrodes can be more restricted and an increase in luminance canbe more achieved than in Example 2. Also, a reduction in display qualitycaused by dark lines can be restricted. Meanwhile, the change inluminance distribution in the diagonal directions is more smoothed inExample 1 than in Example 3 in which the outer peripheral shape of thepositioning areas is a quadrangle as in Example 2. Moreover, in order toprevent color deviation, the complicated planar shapes of the islandelectrodes require formation of an island electrode for each sub-pixelincluded in the pixels constituting the image-providing liquid crystalpanel. The design of the island electrodes thus becomes complicated.

Example 4

Example 4 is a combination of the first electrodes used in Example 1shown in FIG. 3 with the planar shape of the island electrodes and theouter peripheral shape of the apertures provided in the base electrodesof the first electrodes used in Example 3. In Example 4, similarly tothe structure shown in FIG. 4, the outer peripheral shape of thepositioning areas for locating the first electrodes is a hexagon. In aplan view, multiple island electrodes are concentrically arranged fromthe center of a first electrode and thereby surround its base electrode.Similarly to Example 3, the planar shape of the island electrodes andthe outer peripheral shape of the apertures provided in the baseelectrode each include multiple linear portions, and at least one linearportion forms an angle of −30° to +30° with the extending direction D3of the linear electrodes of the second electrode.

Similarly to Example 1, the change in luminance distribution can besmoothed between one first electrode and the adjacent first electrodesin six directions in Example 4. Furthermore, similarly to Example 3, theoccurrence of dark lines between adjacent first electrodes can berestricted and the luminance can be increased. Also, a reduction indisplay quality caused by dark lines can be restricted. Meanwhile,similarly to Example 1, the hexagonal outer peripheral shape of thepositioning areas complicates the relation with the corresponding pixelsconstituting the image-providing liquid crystal panel. Moreover,similarly to Example 3, in order to prevent color deviation, thecomplicated planar shapes of the island electrodes require a complicateddesign.

Example 5

Hereinafter, a liquid crystal display device of Example 5 is describedwith reference to FIG. 28 to FIG. 30. The liquid crystal display deviceof Example 5 has the same structure as that of Example 1 except for thedesign of the lower-layer electrode. The description for the structuressimilar to the liquid crystal display device of Example 1 is omittedhere. FIG. 28 is a schematic plan view showing an example of disposing alower-layer electrode in Example 5. FIG. 29 is a schematiccross-sectional view of the first substrate shown in FIG. 28. FIG. 29 isa schematic cross-sectional view taken along the line X3-X4 in FIG. 28.FIG. 30 is an enlarged schematic cross-sectional view showing a part ofFIG. 29. FIG. 29 and FIG. 30 are each an enlarged view of the firstsubstrate shown in FIG. 2, and the structure from the insulatingsubstrate 11 to the third insulating layer 17 is not shown.

FIG. 28 shows a case where in two adjacent first electrodes as shown inFIG. 4, an island electrode 314Ab is disposed inside an aperture 314Bcprovided in a base electrode 314Ba of a next first electrode 314B. Asshown in FIG. 28, the lower-layer electrode 12 may be formed in a cyclicshape along the outer periphery of the island electrode 314Ab in a planview. As shown in FIG. 28 and FIG. 29, the lower-layer electrode 12 mayoverlap a space between the island electrode 314Ab and the baseelectrode 314Ba in a plan view.

As shown in FIG. 30, the island electrode 314Ab of one first electrodeand the base electrode 314Ba of the next first electrode each form anelectric field with the second electrode 16 stacked with the insulatinglayer 15 in between. The space (gap) between the island electrode 314Aband the base electrode 314Ba tends to have an alignment defect of liquidcrystal molecules. In Example 5, the lower-layer electrode 12 overlapsthe gap. Thus, an electric field is also formed between the lower-layerelectrode 12 and the second electrode 16, and the electric field thuscan change the alignment azimuth of liquid crystal molecules located inthe gap, whereby the occurrence of dark lines can be restricted. InExample 5, in addition to smoothing the change in luminance betweenadjacent first electrodes, the occurrence of dark lines is restrictedand thereby the transmittance of the dimming panel can be improved.Moreover, the restriction of the occurrence of dark lines allows theboundaries between adjacent first electrodes to be less recognizable,which can more improve the display quality of the dimming panel. Example5 can be combined with any of Examples 1 to 4.

Comparative Example 1

The dimming panel used in a liquid crystal display device of ComparativeExample 1 uses quadrangular electrodes having a waving (zigzag)periphery as segment electrodes disposed for the respective dimmingunits. Differently from the examples of the present invention, eachsegment electrode includes no island electrodes and has a structure inwhich the outer peripheries of adjacent segment electrodes are engagedwith each other on the same layer. The liquid crystal display device ofComparative Example 1 is described with reference to FIG. 31 to FIG. 39.The liquid crystal display device of Comparative Example 1 has the samestructure as that of Example 1 except for the structure of the segmentelectrodes, the arrangement of members such as the segment electrodesand the common electrode, and applied voltages, and thus the similardescriptions are omitted here.

FIG. 31 is a schematic plan view of the planar shape of segmentelectrodes used in a dimming panel of Comparative Example 1. FIG. 32 isan enlarged schematic view showing a boundary portion between adjacentsegment electrodes shown in FIG. 31. FIG. 33 is a schematiccross-sectional view of the dimming panel used in Comparative Example 1.In Comparative Example 1, the segment electrodes each provided withmultiple linear electrodes, corresponding to the second electrode ofExample 1, are disposed for the respective dimming units.

As shown in FIG. 31, segment electrodes 416A, 416B, 416C, and 416D aretidily arranged in a plan view. As shown in FIG. 32, the segmentelectrode 416A includes multiple linear electrodes 416Aa and is providedwith slits 416Ab between adjacent linear electrodes 416Aa. The linearelectrodes 416Aa may be electrically connected to each other with, forexample, an electrode connecting portion (not shown) formed on the samelayer. In the boundary portion between the adjacent segment electrodes416A and 416B, the segment electrodes are opposed to each other withtheir outer peripheries engaged with each other.

As shown in FIG. 33, the dimming panel used in the liquid crystaldisplay device of Comparative Example 1 includes a stack sequentiallyincluding a common electrode 414, the insulating layer 15, and a segmentelectrode 416A or 416B from the insulating substrate 11 end. The commonelectrode 414 may be a solid electrode entirely formed on the firstsubstrate 10 except for the portions with contact holes CH4. The commonelectrode 414 is connected to, for example, a common line (not shown)disposed on the outer periphery of the dimming panel, and a constantvoltage is applied to the common electrode. The segment electrode 416Ais connected to the connection line 419 through the contact hole CH4.Although not being shown, the segment electrode 416B is also connectedto another connection line 419 through another contact hole. Eachconnection line 419 is connected to drive circuitry of the liquidcrystal display device. In Comparative Example 1, a common voltage(constant voltage) is applied to the common electrode 414, and apredetermined voltage is applied to each of the segment electrodes bythe drive circuitry, whereby a fringe electric field is formed betweenthe common electrode 414 and the segment electrode.

FIG. 34 is a schematic graph showing a change in luminance distributionof the dimming panel used in the liquid crystal display device ofComparative Example 1. In Comparative Example 1, the boundary portionbetween adjacent segment electrodes has a zigzag shape. As shown in FIG.34, the boundary portion merely has a middle gray scale between the grayscales of adjacent dimming units, and the luminance distribution betweenthe adjacent dimming units changes in steps. The change in luminancedistribution is thus not smooth in comparison with Examples 1 to 5. Thechange in luminance distribution in Comparative Example 1 is discussedwith reference to FIG. 35 to FIG. 38. FIG. 35 is a plan photograph ofthe dimming panel used in Comparative Example 1. FIG. 36 is an enlargedphotograph showing a part of FIG. 35. FIG. 37 is a schematic plan viewfor describing a 176° portion of FIG. 36. FIG. 38 is a schematic planview for describing an 86° portion of FIG. 36.

As shown in FIG. 35, dark lines are recognized in one direction inComparative Example 1. In Comparative Example 1, portions with adjacentsegment electrodes opposed to each other are linearly aligned in a planeof the dimming panel, whereby dark lines are presumably recognized. Asshown in FIG. 32, the linear electrodes of one segment electrode and thelinear electrodes of the next segment electrode are opposed with a spacein between in Comparative Example 1. In a portion (also referred to as agap) where the linear electrodes of the adjacent segment electrodes areopposed, liquid crystal molecules cannot be rotated due to the influenceof fringe electric fields. Thus, the liquid crystal molecules cannot bealigned at a desired azimuth in the gap. The region with such analignment defect of liquid crystal molecules is recognized as a darkline.

Here, the occurrence of dark lines is discussed with reference to FIG.36 that is an enlarged photograph showing a portion of the photographshown in FIG. 35. In FIG. 36, provided that an angle formed by astraight line connecting adjacent gaps and the above 0° reference lineis defined as a gap angle, a dark line is remarkably recognized in aportion with a gap angle of 176° (+96° with respect to the extendingdirection of the linear electrode 416Aa). Meanwhile, no dark line isrecognized in a portion with a gap angle of 86° (+6° with respect to theextending direction of the linear electrode 416Aa).

Here, a portion with a gap angle of 176° and a portion with a gap angleof 86° are compared. As shown in FIG. 37, in a portion with a gap angleof 176°, adjacent gaps are aligned with small intervals and thus theregions with an alignment defect of liquid crystal molecules arerecognized as dark lines. Meanwhile, as shown in FIG. 38, in a portionwith a gap angle of 86°, adjacent gaps are aligned with a greaterinterval. Thus, the regions with an alignment defect of liquid crystalmolecules are scattered and are presumably not recognized as a darkline.

FIG. 39 is a view showing a relation between gap angles and occurrenceof dark lines shown in FIG. 36. In the semicircle shown in FIG. 39, adarker portion indicates more frequent occurrence of remarkable darklines, and a lighter portion indicates less frequent occurrence ofremarkable dark lines. In Comparative Example 1, in a view from thesecond substrate 40 end, the extending direction of the multiple linearelectrodes 416Aa constituting a segment electrode is set to 80° in thecounterclockwise direction with one of the absorption axes of a pair ofpolarizers sandwiching the dimming panel defined as 0°. FIG. 39 alsodemonstrates that the gap angle is preferably an angle of −30° to +30°,more preferably −15° to +15°, with respect to the extending direction ofthe linear electrodes 416Aa.

What is claimed is:
 1. A dimming unit comprising: a dimming panel; anddrive circuitry, the dimming panel sequentially including a firstsubstrate, a liquid crystal layer, and a second substrate, the firstsubstrate sequentially including an insulating substrate, a lower-layerelectrode, a first insulating layer, multiple first electrodes, a secondinsulating layer, and a second electrode which is provided with multipleparallel linear electrodes and to which a constant voltage is applied,the first electrodes each including multiple island electrodes which arespaced from each other in a plan view and are electrically connected toeach other, at least one of the island electrodes being electricallyconnected to the lower-layer electrode through a contact hole, the drivecircuitry controlling voltages applied to the respective firstelectrodes.
 2. The dimming unit according to claim 1, wherein the islandelectrodes are arranged in a manner that an electrode area occupancydecreases toward an outer periphery of each of the first electrodes, atleast one of the island electrodes of a selected electrode of the firstelectrodes is disposed in a position between the island electrodes of anext electrode, and at least one of the island electrodes of the nextelectrode is disposed in a position between the island electrodes of theselected electrode.
 3. The dimming unit according to claim 2, whereinthe lower-layer electrode overlaps a space between the island electrodesof the selected electrode and the island electrodes of the nextelectrode in a plan view.
 4. The dimming unit according to claim 1,wherein at least one of the island electrodes has a quadrangular planarshape.
 5. The dimming unit according to claim 1, wherein at least one ofthe island electrodes has an outer peripheral shape including a linearportion that forms an angle of −30° to +300 with respect to an extendingdirection of the linear electrodes of the second electrode, providedthat in a view seen from a second substrate end, an angle formed in aclockwise direction is defined to be a negative angle and an angleformed in a counterclockwise direction is defined to be a positiveangle.
 6. The dimming unit according to claim 1, wherein at least one ofthe island electrodes has a planar shape including a curved portion. 7.The dimming unit according to claim 1, wherein the first substrateincludes multiple connection lines connecting the respective firstelectrodes and the drive circuitry.
 8. The dimming unit according toclaim 1, wherein each of the first electrodes further includes a baseelectrode provided with multiple apertures, the island electrodessurround the base electrode in a plan view, the base electrode iselectrically connected to the lower-layer electrode through anothercontact hole, at least one of the island electrodes of a selectedelectrode of the first electrodes is disposed in a position inside atleast one of the apertures of a next electrode, and at least one of theisland electrodes of the next electrode is disposed in a position insideat least one of the apertures of the selected electrode.
 9. The dimmingunit according to claim 8, wherein the apertures provided in the baseelectrode are arranged in a manner that an aperture area occupancyincreases from a center toward an outer periphery of the base electrode.10. The dimming unit according to claim 8, wherein the lower-layerelectrode overlaps a space between the apertures provided in the baseelectrode of the selected electrode and the island electrodes of thenext electrode in a plan view.
 11. The dimming unit according to claim8, wherein at least one of the apertures has a quadrangular outerperipheral shape.
 12. The dimming unit according to claim 8, wherein atleast one aperture has an outer peripheral shape including a linearportion that forms an angle of −30° to +30° with respect to an extendingdirection of the linear electrodes of the second electrode, providedthat in a view seen from a second substrate end, an angle formed in aclockwise direction is defined to be a negative angle and an angleformed in a counterclockwise direction is defined to be a positiveangle.
 13. The dimming unit according to claim 8, wherein at least oneof the apertures includes an outer peripheral shape including a curvedportion.
 14. A liquid crystal display device comprising: animage-providing liquid crystal panel; a backlight; and a dimming unitbetween the image-providing liquid crystal panel and the backlight, thedimming unit comprising: a dimming panel; and drive circuitry, thedimming panel sequentially including a first substrate, a liquid crystallayer, and a second substrate, the first substrate sequentiallyincluding an insulating substrate, a lower-layer electrode, a firstinsulating layer, multiple first electrodes, a second insulating layer,and a second electrode which is provided with multiple parallel linearelectrodes and to which a constant voltage is applied, the firstelectrodes including multiple island electrodes which are spaced fromeach other in a plan view and are electrically connected to each other,at least one of the island electrodes being electrically connected tothe lower-layer electrode through a contact hole, the drive circuitrycontrolling voltages applied to the respective first electrodes.
 15. Theliquid crystal display device according to claim 14, wherein theimage-providing liquid crystal panel includes multiple pixels includingsub-pixels of multiple colors and being arranged in a matrix in a plane,and the island electrodes include an overlapping electrode portionoverlapping the sub-pixels of all colors included in one pixel.
 16. Theliquid crystal display device according to claim 15, wherein in theoverlapping electrode portion, a difference between a maximum value anda minimum value among electrode areas overlapping the respectivesub-pixels of the respective colors is 30% or less of the maximum value.17. The liquid crystal display device according to claim 14, wherein theimage-providing liquid crystal panel includes multiple pixels includingsub-pixels of multiple colors and being arranged in a matrix in a plane,and the apertures include an overlapping aperture portion overlappingthe sub-pixels of all colors included in one pixel.
 18. The liquidcrystal display device according to claim 17, wherein in the overlappingaperture portion, a difference between a maximum value and a minimumvalue among aperture areas overlapping the respective sub-pixels of therespective colors is 30% or less of the maximum value.